JP2008189791A - Friction material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain wearing-resistance at a high temperature area, suppression effect of an opposition surface attacking property and suppression effect of noise of a brake even if a lead compound and an antimony compound not preferable in the aspect of environment preservation are not used regarding a friction material utilized for an automotive brake or the like. <P>SOLUTION: Into the raw material composition of the friction material obtained by molding and curing the raw material composition containing a phenol resin added as a fiber base material, a friction adjustment material, a filler and a binder as a main component, preferably 0.1-10.0 vol.% of tungsten sulfide and preferably 5.0-25.0 vol.% of potassium titanate are added. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a friction material used for various brakes, clutch facings, and the like, and particularly to a friction material that is environmentally friendly and excellent in performance.

  Friction materials (such as friction pads for disc brakes and brake linings for drum brakes) used in automobile brakes have conventionally been blended with graphite or molybdenum disulfide to improve wear resistance. Has been done. In addition, it is known that lead compounds and antimony compounds such as lead sulfide, antimony oxide, and antimony sulfide are effective for suppressing the deterioration of the face-to-face attack due to the metal catch generated in a high temperature range. However, there is an increasing trend to suppress the use of lead compounds and antimony compounds due to environmental efforts.

  In order to suppress the use of lead compounds and antimony compounds, alternative materials with low environmental impact are required. Therefore, Patent Document 1 below proposes that three or more kinds of metal sulfides other than titanium sulfide and metal composite sulfides are contained as an alternative material. For the metal sulfides to be contained, zinc sulfide, sulfide Specific examples include copper, bismuth sulfide, tin sulfide, iron sulfide, manganese sulfide, and molybdenum sulfide.

In addition, inorganic fibers and / or inorganic particles other than asbestos 5 to 70% by weight, pulp-like material of para aromatic polyamide polymer 5 to 70% by weight, carbon fiber, carbon black, graphite powder, molybdenum disulfide, disulfide Friction material mainly composed of 1 to 30% by weight of at least one solid lubricant selected from the group consisting of tungsten, boron nitride, nickel iodide, and fluororesin, and 2 to 50% by weight of aromatic polyamide fiber. (See Patent Document 2 below)
Developed friction material (see Patent Document 3 below) that uses metal sulfides such as molybdenum disulfide and tungsten disulfide, and also uses metals such as copper, tin, zinc, nickel, iron, chromium, molybdenum, and tungsten. Has been.
Special table 2003-503555 gazette JP-B-1-48304 JP-A-5-179232

  Patent Document 1 describes that three or more kinds of metal sulfides other than titanium sulfide and metal composite sulfides are contained. However, in the method using only metal sulfides as substitutes for antimony compounds and lead compounds, suppression of metal catch It is difficult to obtain satisfactory performance with respect to wear resistance of the friction material itself and suppression of low frequency noise (low frequency noise generated during braking).

  The friction material of Patent Document 2 also states that the addition of the above-described solid lubricant causes little change in the coefficient of friction due to temperature, has excellent wear resistance, and increases the mechanical strength. Since there are too many, the coating film produced | generated on the surface of (sliding counterpart materials, such as a disc rotor) increases, and brake noise (abnormal noise at the time of braking) generate | occur | produces. In addition, the friction coefficient is significantly reduced due to excessive lubricant.

  Furthermore, the friction material of Patent Document 3 has excellent heat and water fade resistance, and is said to have a stable coefficient of friction even in environments such as high speed, high load, and rainfall. This is a sintered metal friction material. The present invention is not applied to a friction material in which a fiber base material, a friction adjusting material, a filler, or the like is hardened with a resin binder.

  Friction materials made by solidifying fiber base materials, friction modifiers, fillers, etc. with resin binders have less brake noise than sintered metal friction materials, and in particular, NAO (Non-asbestos organic) material is Japan. It is mainstream in Japan.

  The present invention relates to friction materials represented by NAO materials used for automobile brakes and the like, and wear resistance and face-to-face attack at high temperatures without using lead compounds and antimony compounds, which are undesirable in terms of environmental protection. It is an object to be able to obtain an inhibitory effect.

  In order to solve the above-described problems, in the present invention, tungsten sulfide and potassium titanate are used in combination, and the main component thereof is a fiber base material, a friction modifier, a filler, and a phenol resin added as a binder. The raw material composition was added to the raw material composition of the friction material formed and cured.

  Potassium titanate is not limited to a plate shape or flake shape, and a whisker type can also be used.

  Tungsten sulfide is preferably added in an amount of 0.1 to 10.0% by volume, and potassium titanate is preferably added in an amount of 5.0 to 25.0% by volume.

  In the friction material of the present invention, tungsten sulfide and potassium titanate are used in combination as substitutes for lead compounds and antimony compounds, and by adding these two, an appropriate amount of tungsten oxide film is applied to the sliding surface. It is possible to generate (amount that is excessive), and it is possible to obtain a desired wear resistance performance and an effect of suppressing a face-to-face attack by a metal catch while considering environmental problems.

  In addition, by suppressing metal catch, irregular thickness growth and thickness reduction of each part of the sliding surface is suppressed, so judder (judder caused by irregular surface displacement of the sliding surface of the mating material) Suppression is also possible.

  Since potassium titanate is not too hard and is pulverized at the time of friction, low-frequency brake noise (abnormal noise) can be suppressed.

  In addition, in order to obtain stable lubrication performance, it has been conventionally necessary to use several types of lubricants in combination, and the amount used has tended to increase. Since tungsten sulfide having a high concentration is used, the amount of addition can be reduced, leading to cost reduction.

  Note that the friction material in which the addition amounts of tungsten sulfide and potassium titanate are limited to the above-described preferable range exhibits better performance as evidenced by examples described later.

  Hereinafter, embodiments of the friction material of the present invention will be described. The friction material of this invention uses organic and inorganic fibers such as aramid fibers and copper fibers as the fiber base material. Do not use harmful asbestos. Further, graphite, cashew dust, calcium hydroxide, mica, zirconium oxide, barium sulfate, etc. are used as the friction modifier and filler. In addition, potassium titanate and tungsten sulfide, which characterize the present invention, are also added.

  As a binder (binding material) for bonding these raw materials, a thermosetting resin, especially a phenol resin excellent in heat resistance, flame retardancy, mechanical properties, and the like is used. The phenol resin is added with a powder, which is once dissolved and cured.

  In this way, by using tungsten sulfide and potassium titanate in combination, metal catch can be reduced without using lead compounds and antimony compounds, and simultaneously solving environmental problems and suppressing face-to-face attack by metal catch. It becomes possible to do.

  In addition, since the metal catch is suppressed, irregular thickness growth and thickness reduction of each part of the sliding surface are suppressed, so that judder caused by the surface displacement of the sliding surface by the metal catch is also suppressed. .

  In addition, low frequency noise (abnormal noise) during braking can be suppressed by pulverizing potassium titanate during friction.

  In addition, the use of tungsten sulfide having a wide range of lubrication performance from a low temperature region to a high temperature region makes it possible to reduce the amount of lubricant added, leading to cost reduction.

  If the addition amount of tungsten sulfide is less than 0.1% by volume, the effect of addition may be small and the suppression of metal catch may be insufficient. In this case, the friction surface of the counterpart material (for example, the disk rotor) may be insufficient. Since regular wall thickness growth and irregular shaving occur and judder is generated, the addition amount of tungsten sulfide is preferably 0.1% by volume or more. Moreover, if the added amount of tungsten sulfide exceeds 10.0% by volume, an oxide film is excessively formed and adheres to the mating material more than necessary, which increases the tendency to generate low-frequency noise. Therefore, the upper limit of the tungsten sulfide addition amount is preferably limited to 10.0% by volume.

  Further, the potassium titanate used in combination is preferably a plate-like or flake-like one rather than a whisker-type one in view of scattering prevention.

  When the added amount of potassium titanate is less than 5.0% by volume, the grinding effect of the produced coating (working as an abrasive) and the low frequency noise suppression effect due to self-grinding of potassium titanate are small and practical. Fade. On the other hand, if the amount of potassium titanate exceeds 25.0% by volume, the grinding effect of the coating becomes too great, and it becomes difficult to form an appropriate amount of oxide coating on the sliding surface of the counterpart material. It becomes difficult to impart the wear resistance. Moreover, the suppression of the metal catch becomes insufficient, and the difference in the thickness of the friction surface of the mating material grows, and the occurrence of judder can be considered.

  The friction material of the present invention is formed by forming a raw material composition obtained by mixing necessary raw materials at a predetermined ratio by applying predetermined temperature and pressure, and further thermosetting the phenol resin of the binder. Depending on the condition, finish polishing or the like is performed to obtain a desired product such as a friction pad. Molding and curing can be performed by a method as disclosed in Patent Document 1 or a general method for manufacturing a friction material. As for the manufacturing conditions, no special conditions are required, and the conditions disclosed in Patent Document 1 are sufficient.

-Example-
A friction material for performance evaluation was manufactured. Table 1 shows the raw material components of the friction material and the contents of the raw material components. Examples 1 to 23 in Table 1 are invention products, and Comparative Examples 1 to 5 are comparative products. Inventive products and comparative products were made to have the same powder phenolic resin content of fiber base material, graphite, cashew dust, calcium hydroxide, mica, zirconium oxide, and binder, and the additive amount was different from other additive components.

  Table 2 shows the test results of the performance evaluation. For performance evaluation, we conducted a wear test for each temperature, and investigated the occurrence of metal catches, the occurrence of low-frequency noise, and the impact on the environmental load. The test methods and evaluation criteria are summarized below.

・ [Abrasion test]
Measures the amount of wear under conditions of braking initial speed 50 km / h, braking deceleration 0.3 G, braking count 1000 conversion, pre-braking temperature 100 ° C, 200 ° C, 300 ° C, 400 ° C.
・ [Generation of metal catches]
In the above wear test, the occurrence of metal catch was observed when measuring the amount of wear at each temperature, and evaluated according to the following criteria.
A: No metal catch. ○: Several small metal catches with a major axis of 3 mm or less.
Δ: Many small metal catches. X: A large metal catch having a major axis of 5 mm or more.
・ [Average friction coefficient]
Average value of coefficient of friction at the time of the second effect of JASO C406 ・ [Low frequency noise]
40km / h in actual vehicle evaluation, brake temperature before braking 60 ° C, 90 ° C, 120 ° C, 150 ° C, 180 ° C, 150 ° C, 120 ° C, 90 ° C, 60 ° C, braking deceleration 0.2G, 0.3G, At 0.4G, 0.6G, and 0.8G, the sound pressure of low frequency noise of 2 kHz or less when the driver's sensory evaluation is large level x, medium level generation Δ, small level generation ○, no generation ◎.
・ [Thickness difference growth]
Measure the thickness of the friction surface of the disk rotor that is the mating material, and calculate the difference between the maximum and minimum values.
·〔Environmental load〕
If the raw material composition contains an antimony compound even in a very small amount, the impact on the environmental impact is X. Since whisker-like potassium titanate is considered to be scattered in the work environment, it was evaluated as Δ.

-Evaluation-
As can be seen from Table 2, among the invention products, Examples 4 to 4 in which the addition amount of tungsten sulfide was 0.1 to 10.0% by volume and the addition amount of potassium titanate was 5.0 to 25.0% by volume. In the evaluation items 6, 9 to 14, and 17 to 19, there is no evaluation of x in all the evaluation items, and good results are obtained by comprehensive judgment. Among the inventive products, in particular, Examples 4, Examples 10 to 12, and Example 18 have all evaluation items as ◯ and ◎, and also have small thickness difference growth. Recommended.

  The friction material of the present invention is suitable for use as a disk brake friction pad or a drum brake brake shoe with a disk rotor or drum rotor as a counterpart material, but it can also be used for clutch facing and the like. .

Claims (3)

  In a friction material formed by molding and curing a raw material composition mainly composed of a fiber base material, a friction modifier, a filler, and a phenol resin added as a binder, tungsten sulfide and potassium titanate are contained in the raw material composition. A friction material characterized by the addition of each.   2. The friction according to claim 1, wherein the addition amount of tungsten sulfide is 0.1 to 10.0% by volume and the addition amount of potassium titanate is 5.0 to 25.0% by volume relative to the raw material composition. Wood.   The friction material according to claim 1 or 2, wherein organic fibers and inorganic fibers excluding asbestos are used as the fiber base material.